Conventionally, a method of examining the water quality of sea water using an autonomous underwater vehicle that travels through water by means of battery power is known. Naturally, if the residual battery power of the autonomous underwater vehicle drops to zero, it becomes impossible to collect data relating to the water quality or to travel through the water. Because of this, when the residual battery power drops below a specified value, it is normal for the autonomous underwater vehicle to be recovered to a surface vessel so that the battery can be charged.
In this manner, if the autonomous underwater vehicle is recovered to the surface vessel each time the battery needs charging, then both the time required and the costs increase enormously. As a consequence, in recent years, advances have been made in the development of technology to enable this charging to be performed underwater. For example, in Patent document 1 (see below), technology is disclosed in which a battery that is installed in an underwater station that collects data relating to the water quality of sea water is charged by an underwater robot that travels through the water using a wireless power supply system (in particular, an electromagnetic induction system).